CrossID Help

This page is to do dynamic cross identifications of SDSS photometric objects with a
user defined list of object positions or objIDs (5-part SDSS object ID consisting of
run,rerun,camcol,field,obj). You can even join
the upload list with matching spectra (SpecObj) if you want spectroscopic information.
Click here for an example.

In order to avoid congestion on the server, the upload file is limited to a size of 80KB, and the
radius (for RA/dec search) is limited to 3 arcmin. The crossid search will time out
after 600 secs, and the output data set can not exceed 100000
objects.
Please see the Query Limits page. If this is a
problem, please submit your list in pieces.

Upload list format:

You have the following choices:

List of (ra,dec) pairs or list of objIDs (run,rerun,camcol,field,obj)
Always ra comes first, followed by dec. Both ra and dec must be in
degrees. The separator can be any white space or a comma.
The objIDs must be the 5-part SDSS identifiers, i.e. run, rerun,
camcol, field and obj numbers, not the long 64-bit objIDs.

List of preceding non-data fields followed by (ra,dec) or (run,rerun,camcol,field,obj) data fields
The fields must always be in this order. The preceding columns can be any fields that
you want repeated in the output. The number of preceding columns must be specified in
the second parameter above. The default example shows one preceding column ("name").
Both ra and dec must be in degrees. The separator can be any white space or a comma.

Same as above, with a single header line
The formats (1) and (2) can also contain a single header line,
containing the column names. The header must use the same separator as the data.
The names ra and dec or run,rerun,camcol,field and
obj are mandatory.

Lists in the IRSA Gator format
For details see the IRSA website.

You need to either cut/paste the list into the textbox, or upload a text file. Various
extensions (.txt, .dat, .csv, .tbl) are allowed, as long as the MIME type does not get confused.
Binary files are not accepted.

If both the paste buffer and file upload are specified, the file upload takes precedence.

Setting up query in the query window:

Add or remove fields that you want returned from the SELECT list, and add more constraints to the WHERE
clause if you desire (preceded with a boolean operator). If your query does not include a p.objID field in
the SELECT, it will be added for you, because the matching with the upload list is done based on objID. You
may also replace PhotoTag with Galaxy, Star, or any other
photo view or table if you want to restrict the kind of object that is matched. Remember that PhotoTag
will be the fastest usually because it is a thin table (more rows fit in the cache), so unless you need the
fields from larger tables, use PhotoTag (with a mode or type constraint if necessary). Make sure the photo
table/view is aliased as 'p'.
Do not modify the #x and #upload parts of the FROM clause otherwise your upload will
not work.

Using the query window to retrieve spectroscopic information

You can join your upload list with matching spectra (SpecObj table) if desired, by including a join with
the SpecObj table and adding specobj fields to the SELECT list in the query. An example of the
modified query in the query window is shown below (modifications highlighted in bold) which requests the
redshift for each spectrum that matches the imaging object (i.e., SpecObj.bestobjid = PhotoObj.objid).

SELECT

p.objID, p.ra, p.dec,

dbo.fPhotoTypeN(p.type) as type,

p.modelMag_u, p.modelMag_g, p.modelMag_r, p.modelMag_i, p.modelMag_z

, s.z -- return the redshift from matching spectrum

FROM #x x, #upload u, PhotoTag p, SpecObj s

WHERE u.up_id = x.up_id and x.objID=p.objID and s.bestobjid=p.objid

ORDER BY x.up_id

Note that only those objects that have matching spectra in the SpecObj table will be returned in this
case, unless you do a left outer join as follows:

SELECT

p.objID, p.ra, p.dec,

dbo.fPhotoTypeN(p.type) as type,

p.modelMag_u, p.modelMag_g, p.modelMag_r, p.modelMag_i, p.modelMag_z

, ISNULL(s.z,-9999) -- return the redshift from matching spectrum

FROM #x x, #upload u, PhotoTag p

LEFT OUTER JOIN SpecObj s ON s.bestobjid=p.objid

WHERE u.up_id = x.up_id and x.objID=p.objID

ORDER BY x.up_id

This will return all objects with the redshift set to -9999 if there is no matching spectrum (default is 0 without
the ISNULL clause, which is misleading since 0 is a valid redshift value).

The CrossID query is limited to 600 seconds and 100000 rows.
Please see the Query Limits page.